Hold a wake lock while Tor is connected to the internet

This is a partial fix for #314. As noted on that ticket, if a Tor connection is lost for any reason other than the device sleeping, the plugin won't try to replace the lost connection. I'm leaving the ticket open until that more general issue is solved.

The Tor plugin uses several variables to keep track of its connectivity status. This patch refactors those variables into an inner class to improve readability and ensure they're accessed atomically. However, it's still possible for the plugin's state to become inconsistent with the state of the Tor process. For example, calls to updateConnectionStatus() may run concurrently on the IO executor, so their calls to enableNetwork() may be interleaved. As usual, locking would solve this problem but create the potential for deadlock, so I won't try to solve it in this patch.

See merge request !168

Fix name of Tor mobile data setting

Closes #316.

See merge request !167

Reinitialise viewfinder when camera view is shown

Thanks to @str4d for finding the cause of the bug. Closes #331.

See merge request !165

Use Android executor for background API calls

Some Android API calls need to be made from a thread with a message queue, but to keep the UI responsive they shouldn't be made from the UI thread.

This patch gives AndroidExecutor a captive thread with a message queue to execute tasks, and converts various background tasks from creating their own threads to using AndroidExecutor and IoExecutor.

This allows us to upgrade the support library to 23.2.1. Fixes #332.

See merge request !161

Add Snackbar and Toolbar Button to Forum List

This MR is a small change that replaces the custom UI elements in
the forum list with a Snackbar and a Toolbar menu.

It also fixes a background color that was still present with fragment from the NavDrawer.

Before:

![before](/uploads/6dcc545827c035dcffcdf7863893753e/before.png)

After:

![after](/uploads/427de01d8bec779ee81e6ebded3fcd2b/after.png)

It addresses one part (2b) of #305 and is part of #121.


See merge request !163

This commit is a small change that replaces the custom UI elements in
the forum list with a Snackbar and an Toolbar menu.

Addresses one part (2b) of #305

Change the window background system-wide

This also sneaks in some small UI modifications desired by @Megalox.

Closes #307

See merge request !157

Remove old user feedback activity

Fixes #336.

See merge request !162

Don't allow 'this' to escape the constructor

Fixes #325.

See merge request !155

Implement encrypted feedback

Closes #124.

See merge request !138

Closes #307

Migrate crash reports to ACRA

Closes #123.

See merge request !140

Converts the splash screen to XML format

Removes all programatic calls that modify the layout and uses the XML
resource instead.

See merge request !123

Refactor `ContactListAdapter` to be used for Introductions and Forum Sharing

This MR introduces an abstract `BaseContactListAdapter` which provides
most of the adapter logic. The original `ContactListAdapter` extends it to
show date and online status of the contacts.

The new `ContactChooserAdapter` which is used for introductions extends
the `ContactListAdapter` and adds logic for graying out contacts from
different identities than the currently used one.

A new `ContactSelectorAdapter` extends the `BaseContactListAdapter` and
allows to select multiple contacts. It offers a method to return a
collection of all selected `ContactId`s.

Closes #292

See merge request !151

This commit introduces an abstract `BaseContactListAdapter` which provides
most of the adapter logic. The original `ContactListAdapter` extends it to
show date and online status of the contacts.

The new `ContactChooserAdapter` which is used for introductions extends
the `ContactListAdapter` and adds logic for graying out contacts from
different identities than the currently used one.

A new `ContactSelectorAdapter` extends the `BaseContactListAdapter` and
allows to select multiple contacts. It offers a method to return a
collection of all selected `ContactId`s.

This commit also sneaks in an animation when the 'Share Forum' button
is clicked.

Closes #292

Removes all programatic calls that modify the layout and uses the XML
resource instead.